https://doi.org/10.1016/j.seppur.2021.118959
2.3.1. Technical Indicators
Thermal efficiency:
where Lin is the internal mechanical work, in kJ/kg and qin is the heat quantity, in kJ/kg.
Overall efficiency:
where ηmechanic is the mechanical efficiency; ηgenerator is the generator efficiency; and ηboiler is the boiler efficiency.
Overall efficiency of penalties:
where ηoverall_without_CAP is the overall efficiency of steam power plant without chemical absorption process and ηoverall_with_CAP is the overall efficiency of steam power plant with chemical absorption process.
2.3.2. Economic Indicators

Levelized cost of electricity—LCOE;

Capture cost per ton of CO_{2};

Net present value—NPV;

Internal rate of return—IRR;

Discounted payback period—DPP; and

Profitability index—PI.
The LCOE was determined as the sum of investment costs, maintenance costs, and operating costs, relative to the electricity produced and taking into account the devaluation of money in time through the discounted rate considered (Relation (6)). The variable costs of maintenance and operation, respectively, of thermal power plants fitted with capture technology, do not include the CO_{2} transport and storage costs [33].
where LCOE is the levelized cost of electricity, in €/MWh; I is the initial investment in the steam power plant plus the CO_{2} capture technology investment cost, in €; C0 is the operating costs, in €; Cm is the maintenance costs, in €; Cd is the dismantling costs, in €, in this analysis, these costs were considered as 0; r is the discount rate, considered r = 8% (for the energy sector, the discount rate was chosen between 8–12%); and y is the lifetime of the steam power plant, in years, (y∈1 … l). In this study, l was envisioned for 30 years, starting to generate electricity after three years, in the first three years after the investment has been made; and Eel represents the electricity produced in MWh.
To determine the costs associated with the integration of the CO_{2} capture unit into the steam power plant, the CO_{2} capture cost ( Cost_CO2_captured, in €/kgCO_{2}) was calculated with Relation (7) [33]:
where LCOEwith_CAP/ LCOEwithout_CAP is the discounted cost of electricity with and without capture technology, in €/MWh; CO2_captured is the amount of CO_{2} captured, in relation to electricity production (emission factor), in kg/MWh; and CO2_without_CAP/ CO2_with_CAP is the amount of CO_{2} emitted without/with collection technology linked to electricity production, in kg/MWh.
The CO_{2} emissions tax is an indicator that measures the cost avoided thanks to CO_{2} emissions generated in the environment compared to steam power plants without CO_{2} capture technology. The CO_{2} emissions tax is calculated according to the tax per ton of CO_{2} (TCO2) and the quantity of CO_{2} produced from the combustion of the fuel (MCO2) (Relation (8)). The integration of CO_{2} capture technology into the steam plant will therefore reduce CO_{2} emissions considerably and thus increase the cost of electricity produced.
The NPV indicator is calculated as the sum of the annual discounted net income. This indicator is strongly influenced by the delay in updating the net result. In Relation (9), the determination of NPV is shown [34]:
where INy is the income for year y, in €/year; Cy is the operating and maintenance costs for year y, with taxes and duties, but without depreciation, in €/year; Ay is the annuity for year y, in the event of a loan, in €/year; Iy is the equity investment made for year y, in €/year; r is the discount rate for the energy sector between 8 and 12%; l_{f} is the functional life of the steam power plant, in years; and lpi is the initial investment period, in years. For the second amount, if the investment made is not the same each year, the time axis must be taken into account (the time axis of the investment has the opposite meaning to the time axis of the investment project).
The IRR is equal to the discount rate for which the NPV is 0 (Relation (10)) [34].
The DPP (Relation (11)) is the duration after the initial investment is paid back [34].
Relation (12) presents the determination of PI [34].
where NPV is the discounted income, the difference between the discounted revenue, and discounted expenditure; DI is the updated investment; DIN is the discounted income; and DC is the discounted expenditure.
2.3.3. Environmental Indicators
The impact indicators were determined from the emissions identified in the inventory analysis. Equation (13) was used to quantify the impact classes [40].
where Ek is the impact of pollutant k on indicator E, in kg_eq/kg; and mk is the amount of pollutant produced, in kg/FU. For the ADP, mr is the mass of fuel (coal), in kg/FU and Er is the impact of coal on the ADP indicator, in kg_eq/kg (Table 5).
Impact Evaluation  Pollutants  Equation Used  Values 

ADP [kg_Sb_eq/FU] 
–  ADP=∑rADPr×mr ADPr—ADP for each resource “r”, [kg_Sb_eq/kg] mr—quantity used for the resource “r”, [kg/FU] 
ADP_{natural gas} = 0.0187 ADP_{hard coal} = 0.0134 ADP_{lignite} = 0.00678 
GWP [t_CO_{2}_eq/FU]  CO_{2}, CH_{4}, N_{2}O  GWP=∑kGWPk×mk GWPk– GWP for each pollutant “k”, [kg_CO_{2}_eq/kg] mk—quantity used for the pollutant “k”, [kg/FU] 
GWP_{CO2} = 1 GWP_{CH4} = 21 GWP_{N2O} = 310 
AP [t_SO_{2}_eq/FU] 
SO_{2}, NH_{3}, NO_{2}  AP=∑kAPk×mk APk—AP potential for each pollutant “k”, [kg_SO_{2}_eq/kg] mk—quantity used for the pollutant “k”, [kg/FU] 
AP_{SO2} = 1.2 AP_{NH3} = 1.6 AP_{NO2} = 0.5 
POCP [t_C_{2}H_{4}_eq/FU] 
CO, SO_{2}, CH_{4}, CH_{2}O, NO_{2}  POCP=∑kPOCPk×mk POCPk—POCP potential for each pollutant “k”, [kg_C_{2}H_{4}_eq/kg] mk—quantity used for pollutant “k”, [kg/FU] 
POCP_{CO} = 0.027 POCP_{SO2} = 0.048 POCP_{CH4} = 0.006 POCP_{CH2O} = 0.519 POCP_{NO2} = 0.028 
EP [t_PO_{4}^{3−}_eq/FU] 
NO, NH_{3}, NO_{2}, COD, NH_{4}  EP=∑kEPk×mk EPk—EP potential for each pollutant “k”, [kg_PO_{4}^{3−}_eq/kg] mk —quantity used for the pollutant “k”, [kg/FU] 
EP_{NO} = 0.2 EP_{NH3} = 0.35 EP_{NO2} = 0.13 EP_{COD} = 0.022 EP_{NH4} = 0.35 
HTP [t_1.4DCB_eq/FU] 
SO_{2}, NH_{3}, NO_{2}, Dust, CH_{2}O, Pb, Phenol, HCl, HF  HTP=∑k∑comHTPcom,k×mcom,k com: compartment (air, water soil); HTPcom,k—HTP potential for each pollutant “k”, and for each compartment, [kg_1.4DCB_eq/kg] mcom,k—quantity used for the pollutant “k” and compartment, [kg/FU] 
HTP_{SO2} = 0.096 HTP_{NH3} = 0.1 HTP_{NO2} = 1.2 HTP_{Dust} = 0.82 HTP_{CH2O} = 0.83 HTP_{Pb} = 3300 HTP_{Phenol} = 0.52 HTP_{HCl} = 0.5 HTP_{HF} = 94 